FILE - In this Sept. 23, 1955, file photo, J.W. Milam, left, his wife, second left, Roy Bryant, far right, and his wife, Carolyn Bryant, sit together in a courtroom in Sumner, Miss. Bryant and his half-brother Milam were charged with murder but acquitted in the kidnap-torture slaying of 14-year-old black teen Emmett Till in 1955 after he allegedly whistled at Carolyn Bryant. The men later confessed in a magazine interview but weren’t retried; both are now dead. Citing "new information," the U.S. Justice Department has reopened the investigation into Till's death. (AP Photo, File)

FILE - In this 1955 file photo, Carolyn Bryant poses for a photo. A Justice Department report to Congress says the agency is reinvestigating the 1955 slaying of Emmett Till, a black teenager whose brutal killing in Mississippi after receiving what it calls "new information." The report doesn't say what any potential new evidence might be. But it follows the publication of a book which included passages where Donham, then known as Carolyn Bryant and a potential witness at the time, acknowledged lying. (AP Photo/Gene Herrick, File)

FILE - This undated photo shows Emmett Louis Till, a 14-year-old black Chicago boy, who was kidnapped, tortured and murdered in 1955 after he allegedly whistled at a white woman in Mississippi. The federal government has reopened its investigation into the slaying of Till, the black teenager whose brutal killing in Mississippi helped inspire the civil rights movement more than 60 years ago. (AP Photo, File)

BIRMINGHAM, Ala. (AP) — A 2017 book that revealed lies by a key figure in the Emmett Till case has prompted the U.S government to renew its investigation into the brutal 1955 slaying, a federal official said Thursday.

The reopening of the case had stayed quiet until the contents of a federal report came to light earlier in the day. Till relatives and social justice activists welcomed a fresh look at the killing that shocked the country and stoked the civil rights movement, but acknowledged that the passage of time could hamper justice.

Hours after news broke about the renewed investigation, a federal official familiar with the matter told The Associated Press that information in the 2017 book was what led federal investigators to re-examine the case. The official wasn't authorized to discuss the matter publicly and spoke to AP on condition of anonymity.

The book "The Blood of Emmett Till" by Timothy B. Tyson quotes a white woman, Carolyn Donham, as saying during a 2008 interview that she wasn't truthful when she testified that the black teen grabbed her, whistled and made sexual advances at a Mississippi store six decades ago.

Tyson told reporters Thursday that he was contacted by the FBI weeks after his book was published in January 2017, and he furnished them interview recordings and other research materials. He doesn't think his research alone would support new charges but said investigators may be able to link it to other material in their possession.

"It's possible that the investigation will turn up something. But there's nothing that I know of, and nothing in my research, that is actionable, I don't think," he said. "But I'm not an attorney or a detective."

The reopening of the Till case was disclosed in a federal report sent to lawmakers in March that said the Justice Department had received unspecified "new information." The report's contents weren't widely known until Thursday.

A potential witness with the 14-year-old Till in the store that day, cousin Wheeler Parker, said Thursday that he has talked with law enforcement about the case in recent months.

The prosecutor with jurisdiction over the Mississippi community where Till was abducted, District Attorney Dewayne Richardson, declined to comment on whether federal authorities had given him new information since they reopened the investigation. The Justice Department also declined to comment.

It's unclear what new charges could result from a renewed investigation, said Tucker Carrington, a professor at the University of Mississippi law school.

Conspiracy or murder charges could be filed if anyone still alive is shown to have been involved, he said, but too much time likely has passed to prosecute anyone for other crimes, such as lying to investigators or in court.

The case was closed in 2007 with authorities saying the suspects were dead.

Two white men — Donham's then-husband, Roy Bryant, and his half brother, J.W. Milam — were charged with murder but acquitted in the slaying of Chicago teen Till, who had been staying with relatives in northern Mississippi at the time. The men later confessed to the crime in a magazine interview but weren't retried. Both are now dead.

Donham, who turns 84 this month, lives in Raleigh, North Carolina. A man who came to the door at her residence declined to comment about the FBI reopening the investigation.

The government has investigated 115 cases involving 128 victims under the "cold case" law named for Till, the March federal report said. Only one resulted in in a federal conviction since the act became law.

Deborah Watts, co-founder of the Emmett Till Legacy Foundation, said it's "wonderful" her cousin's killing is getting another look but she didn't want to discuss details.

"None of us wants to do anything that jeopardizes any investigation or impedes, but we are also very interested in justice being done," she said.

Abducted from the home where he was staying, Till was beaten and shot, and his body was found weighted down with a cotton gin fan in a river. His mother, Mamie Till Mobley, had his casket left open. Images of his mutilated body gave witness to the depth of racial hatred in the Deep South and inspired civil rights campaigns.

Donham, then 21 and known as Carolyn Bryant, testified in 1955 as a prospective defense witness in the trial of Bryant and Milam. With jurors out of the courtroom, she said a "nigger man" she didn't know took her by the arm in the store.

"He said, 'How about a date, baby?'" she testified, according to a trial transcript released by the FBI a decade ago. Bryant said she pulled away, and moments later the young man "caught me at the cash register," grasping her around the waist with both hands and pulling her toward him.

A judge ruled the testimony inadmissible. An all-white jury freed her husband and the other man even without it.

In the book, author Tyson wrote that Donham told him her testimony about Till accosting her wasn't true.

"Nothing that boy did could ever justify what happened to him," the book quotes her as saying.